High-power external cavity tunable quantum cascade laser output module

Abstract

The invention provides a high-power external cavity tunable quantum cascade laser output module. The high-power external cavity tunable quantum cascade laser output module comprises a first lens, a first half-wave plate and a first mid-infrared grid polaroid which are sequentially arranged along a light path of a first laser; a second lens, a second half-wave plate, a second mid-infrared grid polarizer and a third half-wave plate are sequentially arranged along the light path of the second laser; emergent light of the first mid-infrared grid polaroid and the third half-wave plate is converged on different surfaces of the third mid-infrared grid polaroid, the first blazed grating is arranged on a reflection light path of the first mid-infrared grid polaroid, and the second blazed grating is arranged on a reflection light path of the second mid-infrared grid polaroid. According to the invention, the problems of wavelength locking and low polarization beam combination efficiency caused by insufficient polarization state of the quantum cascade laser can be effectively solved, narrow linewidth output and wavelength tuning of the quantum cascade laser can be realized, and even high-power dual-wavelength tunable output can be realized through polarization beam combination structure expansion.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor laser technology, in particular to a high-power external cavity tunable quantum cascade laser output module. Background Art

[0002] Quantum cascade lasers have garnered considerable attention from researchers since their successful development by Faist et al. at Bell Labs. This is because, unlike conventional semiconductor lasers, they rely on a light emission process independent of the semiconductor bandgap, enabling laser output from the mid-infrared to the terahertz band. In particular, they cover the two critical atmospheric windows of 3-5μm and 8-12μm, offering significant application value in free-space communications and trace gas detection. However, conventional quantum cascade lasers, which typically output multiple longitudinal modes and have low power, struggle to meet practical application requirements. This, in turn, places new demands on the power, linewidth, and tuning range of quantum cascade lasers.

[0003] There are currently three ways to achieve wavelength tuning: DBR grating, DFB grating and tuning using an external cavity. Compared to the above two methods, the external cavity feedback quantum cascade laser does not require too high a design of the light source itself, and can achieve single longitudinal mode, wide tuning laser output, so it can meet the above requirements. Typical external cavity feedback quantum cascade lasers can be divided into Littrow (such as Figure 5 Compared to the Littrow structure, the Littman structure has an additional reflector. Although it can achieve a narrower linewidth, it also increases the loss.

[0004] However, the power of quantum cascade lasers is low and the polarization degree is less than 100% (e.g. Figure 4 As shown, the output beam is not fully polarized and depolarization occurs at high currents, which does not match the polarization characteristics of the blazed grating. This is not conducive to subsequent power scaling and limits the further application of this technology.

[0005] To this end, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-power external cavity tunable quantum cascade laser output module, which can effectively solve the problems of wavelength locking and low polarization beam combining efficiency caused by insufficient polarization state of quantum cascade lasers, and can achieve high-power dual-wavelength tunable output by expanding the polarization beam combining structure; The present invention provides a high-power external cavity tunable quantum cascade laser output module, comprising: a first laser, wherein a first lens, a first half-wave plate, and a first mid-infrared wire grating polarizer are sequentially arranged along the optical path of the first laser; a second laser, wherein a second lens, a second half-wave plate, a second mid-infrared wire grating polarizer, and a third half-wave plate are sequentially arranged along the optical path of the second laser; and a third mid-infrared wire grating polarizer, wherein the output light of the first mid-infrared wire grating polarizer and the third half-wave plate are respectively converged onto different surfaces of the third mid-infrared wire grating polarizer.

[0007] Furthermore, by setting the tilt angle of the third mid-infrared grating polarizer, the transmitted light of the outgoing light of the first mid-infrared grating polarizer passing through the third mid-infrared grating polarizer and the reflected light of the outgoing light of the third half-wave plate on the surface of the third mid-infrared grating polarizer can be combined.

[0008] Furthermore, it includes a first blazed grating and a second blazed grating, wherein the first blazed grating is arranged on the reflected light path of the first mid-infrared grating polarizer, and the second blazed grating is arranged on the reflected light path of the second mid-infrared grating polarizer.

[0009] Furthermore, the installation angles of the first blazed grating and the second blazed grating are both adjustable.

[0010] Furthermore, the blaze angle of the blazed grating is placed at the Littrow angle.

[0011] Furthermore, both the first laser and the second laser are quantum cascade lasers.

[0012] Furthermore, the first laser and the second laser are fixed on an aluminum substrate that has been anodized, and an indium sheet is provided between the bottom of the laser and the aluminum substrate.

[0013] Furthermore, both the first lens and the second lens are aspherical lenses.

[0014] Furthermore, both surfaces of the first lens and the second lens are coated with anti-reflection films.

[0015] Furthermore, the first half-wave plate, the second half-wave plate and the third half-wave plate are all rotatable half-wave plates.

[0016] The technical solution of the present invention involves collimating the light beam emitted by a first laser through a first lens and then incident on a first half-wave plate placed before a first mid-infrared grid polarizer. This adjusts the P and S light components in the beam. As the beam enters the first mid-infrared grid polarizer, the S light is unable to pass through the polarization separation film and is totally reflected, while the P light is directly transmitted and output, and then incident on a third mid-infrared grid polarizer again. Separately, the light beam emitted by a second laser is collimated by a second lens and similarly polarized by the second mid-infrared grid polarizer. The P light output branch is converted to S light by a third half-wave plate. The P light that passes through the first mid-infrared grid polarizer is transmitted by the third mid-infrared grid polarizer, while the S light that passes through the third half-wave plate is reflected by the third mid-infrared grid polarizer. Polarization beam combination is then performed there, resulting in high-power output. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 is a schematic diagram of the aspheric lens of the present invention; Figure 3 Schematic diagram of the laser polarization beam combining of two lasers of the present invention; Figure 4 Schematic diagram of traditional polarization beam combining in background technology; Figure 5 Schematic diagram of the structure of a traditional Littrow external cavity tunable quantum cascade laser in the background technology; Description of reference numerals: 11-first laser; 12-second laser; 21-first lens; 22-second lens; 31-first half-wave plate; 32-second half-wave plate; 33-third half-wave plate; 41 - first mid-infrared grid polarizer; 42 - second mid-infrared grid polarizer; 43 - third mid-infrared grid polarizer; 51-first blazed grating; 52-second blazed grating. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0022] Example 1 like Figure 1-Figure 3 As shown, the present invention provides a high-power external cavity tunable quantum cascade laser output module, comprising: a first laser 11, wherein a first lens 21, a first half-wave plate 31, and a first mid-infrared wire grid polarizer 41 are sequentially provided along the optical path of the first laser 11; a second laser 12, wherein a second lens 22, a second half-wave plate 32, a second mid-infrared wire grid polarizer 42, and a third half-wave plate 33 are sequentially provided along the optical path of the second laser 12; and a third mid-infrared wire grid polarizer 43, wherein the outgoing light of the first mid-infrared wire grid polarizer 41 and the third half-wave plate 33 are respectively converged onto different surfaces of the third mid-infrared wire grid polarizer 43.

[0023] The angle of the third mid-infrared grid polarizer 43 is such that the light transmitted by the first mid-infrared grid polarizer 41 is transmitted and the light transmitted by the third half-wave plate 33 is reflected, thereby achieving beam combination. The mid-infrared grid polarizer is based on silicon and is used to achieve polarization separation and beam combination.

[0024] The system also includes a first blazed grating 51 and a second blazed grating 52. The first blazed grating 51 is disposed in the reflected light path of the first mid-infrared wire grid polarizer 41, and the second blazed grating 52 is disposed in the reflected light path of the second mid-infrared wire grid polarizer 42. Both the first blazed grating 51 and the second blazed grating 52 are mounted with adjustable angles. The blazed angle of each blazed grating is optimized for the central wavelength band of the quantum cascade laser, and the blazed gratings are positioned at the Littrow angle, forming an optical feedback channel. Blazed gratings are used for wavelength locking and wavelength tuning of quantum cascade lasers. For S-light, which cannot pass through the polarization separation film, it is totally reflected by the mid-infrared wire grid polarizer and incident on the blazed grating positioned at the Littrow angle, forming optical feedback, achieving narrowed linewidth and high side mode suppression ratio. The selected wavelength can be changed by changing the grating angle. By fixing the angle of one grating and adjusting the angle of the other, high-power dual-wavelength tunable output can be achieved.

[0025] The first laser 11 and the second laser 12 are both quantum cascade lasers. The quantum cascade lasers are packaged in a Window package and fixed on an anodized aluminum substrate. Indium sheets are placed at the bottom and between the aluminum substrate to fully dissipate heat.

[0026] The first lens 21 and the second lens 22 are both aspherical lenses. Aspherical lenses can minimize spherical aberration. At the same time, both surfaces of the aspherical lenses (the first lens 21 and the second lens 22) are coated with corresponding anti-reflection coatings.

[0027] The first half-wave plate 31, the second half-wave plate 32, and the third half-wave plate 33 are all rotatable half-wave plates. Rotatable half-wave plates, also known as phase retarders, can cause a certain phase delay in the two polarization states of light in a light beam, thereby changing the polarization state of the light beam by changing the angle between the optical axis and the electric field direction of the output light beam.

[0028] Working principle of the present invention: The light beam emitted by the first laser 11 (quantum cascade laser) is collimated by the first lens 21 (aspheric lens) and then enters the first half-wave plate 31 (rotatable half-wave plate) placed in front of the first mid-infrared wire grid polarizer 41. Rotation of the half-wave plate adjusts the P and S light components / ratios in the beam. As the light beam enters the first mid-infrared wire grid polarizer 41, it performs polarization separation and beam combining. The S light, unable to pass through the polarization separation film, undergoes total internal reflection and enters the first blazed grating 51 positioned at the Littrow angle, forming optical feedback. This achieves linewidth narrowing and a high side-mode suppression ratio. The selected wavelength can be changed by varying the grating angle. The P light is then transmitted directly out and enters and passes through the third mid-infrared wire grid polarizer 43.

[0029] Similarly, the beam emitted by the second laser 12 (quantum cascade laser) is collimated by the second lens 22 (aspheric lens). It is then polarized and separated by the second mid-infrared wire grid polarizer 42. The S-light is then totally reflected and directed into the second blazed grating 52 positioned at the Littrow angle for external cavity feedback. However, to achieve polarization beam combining, a third half-wave plate 33 (rotatable half-wave plate) is inserted into the P-light output branch to convert the P-light into S-light. This is then polarized and combined with the P-light that previously passed through the first and third mid-infrared wire grid polarizers 41 and 43, achieving high-power output.

[0030] In addition, by fixing the angle of one blazed grating and adjusting the angle of the other blazed grating, high-power dual-wavelength tunable output can be achieved.

[0031] The present invention can effectively solve the problems of wavelength locking and low polarization combining efficiency caused by insufficient polarization state of quantum cascade lasers, and can realize narrow linewidth output and wavelength tuning of quantum cascade lasers, and can even realize high-power dual-wavelength tunable output through the expansion of polarization combining structure.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-power external cavity tunable quantum cascade laser output module, characterized in that: include: a first laser, wherein a first lens, a first half-wave plate, and a first mid-infrared wire grid polarizer are sequentially arranged along the optical path of the first laser; a second laser, wherein a second lens, a second half-wave plate, a second mid-infrared wire grid polarizer, and a third half-wave plate are sequentially provided along the optical path of the second laser; A third mid-infrared wire grid polarizer, wherein the outgoing light of the first mid-infrared wire grid polarizer and the third half-wave plate are respectively converged on different surfaces of the third mid-infrared wire grid polarizer.

2. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that: By setting the tilt angle of the third mid-infrared grating polarizer, the transmitted light of the outgoing light of the first mid-infrared grating polarizer passing through the third mid-infrared grating polarizer and the reflected light of the outgoing light of the third half-wave plate on the surface of the third mid-infrared grating polarizer can be combined.

3. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that: It also includes a first blazed grating and a second blazed grating, wherein the first blazed grating is arranged on the reflected light path of the first mid-infrared grid polarizer, and the second blazed grating is arranged on the reflected light path of the second mid-infrared grid polarizer.

4. The high-power external cavity tunable quantum cascade laser output module according to claim 3, characterized in that: The installation angles of the first blazed grating and the second blazed grating are adjustable.

5. The high-power external cavity tunable quantum cascade laser output module according to claim 4, characterized in that: The blaze angle of the blazed grating is placed at the Littrow angle.

6. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that: The first laser and the second laser are both quantum cascade lasers.

7. The high-power external cavity tunable quantum cascade laser output module according to claim 6, characterized in that: The first laser and the second laser are fixed on an aluminum substrate that has been subjected to anodizing treatment, and an indium sheet is arranged between the bottom of the laser and the aluminum substrate.

8. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that: Both the first lens and the second lens are aspherical lenses.

9. The high-power external cavity tunable quantum cascade laser output module according to claim 8, characterized in that: Both surfaces of the first lens and the second lens are coated with antireflection films.

10. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that: The first half-wave plate, the second half-wave plate and the third half-wave plate are all rotatable half-wave plates.

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